Detection and quantification of M-proteinemia: comparison of various methods for serum protein electrophoresis.

Background: Detection and quantification of monoclonal proteins is hampered when the monoclonal peak coincides with one of the regular bands in serum proteinelectrophoresis. The objective of this study was to evaluate four procedures for serum proteinelectrophoresis with respect to detection and quantification of monoclonal proteins. Methods: For 466 patient samples with a monoclonal protein, three variants of agarose gel electrophoresis (5-band, split-beta and high resolution) and one variant of capillary electrophoresis were compared with the results of the routinely used agarose gel electrophoresis followed by immunofixation analysis using specific or pentavalent antisera. Results: In total, 310 patient samples were analyzed by the four methods, consisting of 295 samples with a monoclonal protein, seven with oligoclonal bands and eight without any bands. Suspicion of a monoclonal protein was raised in 295/256/256/232/265 of the samples using the reference/5-band/split-beta/high resolution/capillary procedure. In 152/147/135/142/126 of the samples the concentration of monoclonal protein was >1.0 g/L and in 51/33/53/33/67 of the cases, the monoclonal protein was not separated from one of the normal protein zones. Conclusions: In high resolution agarose gel electrophoresis, monoclonal bands of low concentration often remain undetected. In split-beta agarose gel electrophoresis as well as capillary electrophoresis monoclonal bands more often were not separated from the regular protein bands.